Option 1: You can leave it on the grass at the start/finish. There were about 12 bikes left here but I felt a little nervous at using this option.
Option 2: There are fences all over the park, but the closest is the one that surrounds the playground near the start/finish (I went for this option).
Option 3: There are cycle racks about 200 metres south of the start line, roughly in the centre of the park.
Option 4: There are a few more cycle racks and another playground with a fence at the cafe in the park. (not quite as close to the start/finish but good if you're going to the cafe afterwards).
The start of the run is on the grass adjacent to the car park so is pretty convenient for those that arrive by car. The park was being used by lots of football teams for training, and there were a few walkers (but no dog related problems as far as I could see).
There are toilets somewhere near the start but as I didn't use them I can't tell you what they were like. Tarmac makes up about 90% of the surface but the beginning, middle and end are on the grass start/finish area. It's an undulating course, but fairly gentle.
The route has been very well thought out and gives you the opportunity to explore the whole of the park. Firstly you'll head slightly downhill along the central avenue of the park where at the end you'll turn right, pass the Potomac (fish pond) and follow the path around the perimeter of the western half - to give you an idea of size, this half houses 36 football pitches. The path takes you on a long gentle incline and will wear you down if you don't manage your pace. At the end of this half you'll hit the half-way point (complete with half-way timer) and then go back through the start line.
About 80 metres after crossing the the start line for the second time, you'll swing a left and start to explore to eastern side of the park. Here you'll pass the stunning round pond, the cafe, miniature golf course and the mansion (which is the home to the Gunnersbury park museum). The paths meander more in this half of the park and is prettier than the the west side. There are still ups and downs as you progress through this side, and the very last section has you running back towards the start/finish area in the opposite direction that you ran at the start (which means it's uphill).
It is definitely worth mentioning the condition of the tarmac paths. They are not quite as smooth as they once would have been and are clearly due for some maintenance. Saying that, as long as you keep an eye on where you are running you should be fine. The condition of the paths is a sign that this wonderful park has been neglected and as such some of the magnificent buildings are on the English Heritage at risk register, which really is a shame because our parks deserve to be preserved for us and future generations to enjoy.
Fortunately the neglected parts do not spoil the overall parkrun experience. It regularly attracts over 200 runners (exactly 200 on the day I visited) and after my visit I can really see why they come here. For the record, despite the bad condition of the tarmac this course would be fine, but perhaps a little bumpy, for a spot of buggy running. The volunteers are spectacular and I thank you all for making me feel so welcome.
